FIGS. 1, 2, 3, and 4 depict a known automatic recharging dehydrating breather 100, i.e., the ARDB2 manufactured by Waukesha Electric Systems, Inc. (Waukesha, Wis.). The dehydrating breather 100 typically removes moisture from the air of load tap changer tanks, conservators, sealed tanks, control cabinets and the like. For convenience, the operation of the dehydrating breather 100 will be described with reference to a load tap changer tank which stores oil used to cool the tap changer.
A headspace of the tank of the load tap changer (not shown) is connected to the dehydrating breather 100 by a pipe, tube, hose, etc. When the tank exhales, air flows from the headspace of the tank, through the hose, and into the dehydrating breather 100, which vents the air to the atmosphere. When the tank inhales, air is drawn into the dehydrating breather 100 and passes through a desiccant, then through the hose to the tank. The desiccant dehumidifies the air provided to the tank, and, over time, typically becomes saturated with water. The dehydrating breather 100 removes the water absorbed by the desiccant using a process called recharging or regeneration. During a regeneration cycle, an electric heating element, disposed inside the dehydrating breather 100, evaporates the water from a silica gel desiccant, and an embedded PC board ensures that regeneration occurs only during tank exhalation.
FIG. 5 depicts a cross-sectional view of a dehydrating breather 100, annotated to identify the various components, air flows and water flow. The dehydrating breather 100 typically includes a bottom molding with a condensate water filter vent (water drain), a tube and a top molding with the PC board and a top cap.
The top molding includes slots through which air is normally drawn into and expelled from the dehydrating breather 100 through a slot. During regeneration, the heating elements evaporate the water absorbed by the silica gel desiccant, which condenses on the inner surface of the tube, drains to the bottom molding and passes through the filter vent.
During cold weather operation, particularly when the ambient air temperature falls below 32° F., water in the filter vent can typically freeze, which prevents additional condensate from draining out and eventually renders the dehydrating breather 100 inoperable due to the build-up of water within the desiccant chamber.
Accordingly, a low cost and/or low complexity solution to prevent the filter vent from freezing is needed.